#include <u.h>#include <libc.h>#include <ip.h> uchar classmask[4][16] = {	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0x00,0x00,0x00,	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0x00,0x00,0x00,	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0x00,0x00,	0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0xff,  0xff,0xff,0xff,0x00,}; uchar*defmask(uchar *ip){	return classmask[ip[IPv4off]>>6];} voidmaskip(uchar *from, uchar *mask, uchar *to){	int i; 	for(i = 0; i < IPaddrlen; i++)		to[i] = from[i] & mask[i];}